The present invention relates to a catalyst, a method for making the catalyst and a polymerization process employing the catalyst.
In the field of catalytic polymerization of olefins such as propylene to produce useful solid polymers, a continuing objective is to increase productivity. By productivity is meant the amount of useful solid polymer that is obtained by means of a given quantity of catalytic materials. This is important because the removal of catalytic materials from the solid polymer is almost always necessary and is generally troublesome or expansive to carry out. Thus, improved polymerization processes are desired in which the productivity of the polymer per unit of catalyst material is so great that the amount of catalyst residues remaining in the polymer is insignificant and the catalyst removal steps can be minimized or omitted.
One known catalyst system which is said to exhibit a relatively high productivity employs two components wherein the first component is prepared from materials such as titanium tetrachloride, ethyl benzoate, and magnesium chloride and the second component is prepared from materials such as triethylaluminum and ethyl anisate. Such a catalyst system is said to produce large quantities of solid polymer per unit of catalyst.
It is known that an improvement in the type of catalyst represented above is alleged by the incorporation of a solid organic material into the first component which is inert to the catalyst component. An example of such a material is durene. The incorporation of a material such as durene is said to improve the stereospecific nature of the catalyst and provide yet a higher yield of usable polymer per unit of catalyst.
The present invention provides still higher yields of usable polymer per unit of catalyst as compared to the above known catalysts.